This invention relates to an engine control and more particularly to an arrangement and method for controlling the fuel injection system of an internal combustion engine.
In the interest of improving engine performance, fuel economy and exhaust emission control it has been proposed to employ fuel injection systems rather than carburetors. With fuel injection systems, the amount of fuel flowing to the engine can be much more accurately controlled, particularly on a cycle by cycle basis. Thus, fuel injectors are gaining preference in their utilization for engine charge forming systems.
Although fuel injectors have an advantage over carburetors in many regards, there is one area where the fuel injector does have a disadvantage relative to a carburetor. This deals with the stopping of an engine and the subsequent restarting of the engine. For a variety of reasons, there are certain advantages to supplying the fuel to the engine through its induction system rather than directly into the combustion chamber. One disadvantage with this type of arrangement is, however, when the engine is shut down. This is also the area where fuel injection systems have a disadvantage relative to carburetors.
For cost and other reasons, it has been the preferred practice to employ injection systems where the fuel is injected into the induction system rather than directly into the combustion chamber. Such induction systems are referred to as "manifold induction" systems. When the engine is provided with a manifold or induction system injection system, there is some delay before the fuel charge actually reaches the combustion chambers. If, however, a certain amount of residual fuel is permitted to remain in the induction path after engine shut down, then restarting can be facilitated without requiring excess enrichment to effect the restarting.
With a conventional, carbureted engine, the ignition system is shut off or disabled to stop the engine. The engine will, however, rotate for a number of revolutions after the ignition is stopped due to its rotational inertia. When a carburetor is provided, the air flow through the carburetor will cause additional fuel to be drawn into the induction system and even into the combustion chamber. Hence, restart up is greatly facilitated, particularly when the engine is restarted after a short time interval.
It has been the practice, however, with fuel injection systems to shut off the fuel injection at the same time the engine is disabled. This is possible with most widely used injection systems since the fuel injectors are also electrically controlled.
When a fuel injected engine is shut off, therefore, the fuel flow stops and the engine continues to rotate. This means that any residual fuel in the intake passage will be pumped out of the exhaust and will not remain in the intake passage or combustion chamber. Thus, restarting is difficult with this type of arrangement.
It is, therefore, a principal object of this invention to provide an improved engine control and method particularly adapted for facilitating the restarting of engines.
It is a further object of this invention to provide an improved engine control method for a fuel injected engine wherein restarting is facilitated.
These problems are true with all engines. However, with two cycle crankcase compression engines the problem is even more acute. This is because the induction passage is much longer and there is a greater time interval on restarting for a combustible mixture to finally reach the combustion chamber.